From 91a6866265602a16fd6adfa2c3e35f1adc8d0306 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Herm=C3=A8s=20B=C3=A9lusca-Ma=C3=AFto?=
 <hermes.belusca-maito@reactos.org>
Date: Wed, 26 Aug 2015 00:37:50 +0000
Subject: [PATCH] [NTVDM] Introduce a function for doing guest-to-guest memory
 copies (given here in a temporary implementation until a proper one is
 developed). It will be used in my next commit.

svn path=/trunk/; revision=68826
---
 reactos/subsystems/mvdm/ntvdm/memory.c | 64 +++++++++++++++++++++++---
 reactos/subsystems/mvdm/ntvdm/memory.h | 10 ++++
 2 files changed, 68 insertions(+), 6 deletions(-)

diff --git a/reactos/subsystems/mvdm/ntvdm/memory.c b/reactos/subsystems/mvdm/ntvdm/memory.c
index 692cc526ff8..a07e1fe2218 100644
--- a/reactos/subsystems/mvdm/ntvdm/memory.c
+++ b/reactos/subsystems/mvdm/ntvdm/memory.c
@@ -109,9 +109,7 @@ MemFastMoveMemory(OUT VOID UNALIGNED *Destination,
 #endif
 }
 
-static
-inline
-VOID
+static inline VOID
 ReadPage(PMEM_HOOK Hook, ULONG Address, PVOID Buffer, ULONG Size)
 {
     if (Hook && !Hook->hVdd && Hook->FastReadHandler)
@@ -122,9 +120,7 @@ ReadPage(PMEM_HOOK Hook, ULONG Address, PVOID Buffer, ULONG Size)
     MemFastMoveMemory(Buffer, REAL_TO_PHYS(Address), Size);
 }
 
-static
-inline
-VOID
+static inline VOID
 WritePage(PMEM_HOOK Hook, ULONG Address, PVOID Buffer, ULONG Size)
 {
     if (!Hook
@@ -215,6 +211,62 @@ VOID FASTCALL EmulatorWriteMemory(PFAST486_STATE State, ULONG Address, PVOID Buf
     }
 }
 
+VOID FASTCALL EmulatorCopyMemory(PFAST486_STATE State, ULONG DestAddress, ULONG SrcAddress, ULONG Size)
+{
+    /*
+     * Guest-to-guest memory copy
+     */
+
+    // FIXME: This is a temporary implementation of a more useful functionality
+    // which should be a merge of EmulatorReadMemory & EmulatorWriteMemory without
+    // any local external buffer.
+    // NOTE: Process heap is by default serialized (unless one specifies it shouldn't).
+    static BYTE StaticBuffer[8192]; // Smallest static buffer we can use.
+    static PVOID HeapBuffer = NULL; // Always-growing heap buffer. Use it in case StaticBuffer is too small.
+    static ULONG HeapBufferSize = 0;
+    PVOID LocalBuffer;              // Points to either StaticBuffer or HeapBuffer
+
+    if (Size <= sizeof(StaticBuffer))
+    {
+        /* Use the static buffer */
+        LocalBuffer = StaticBuffer;
+    }
+    else if (/* sizeof(StaticBuffer) <= Size && */ Size <= HeapBufferSize)
+    {
+        /* Use the heap buffer */
+        ASSERT(HeapBufferSize > 0 && HeapBuffer != NULL);
+        LocalBuffer = HeapBuffer;
+    }
+    else // if (Size > HeapBufferSize)
+    {
+        /* Enlarge the heap buffer and use it */
+
+        if (HeapBuffer == NULL)
+        {
+            /* First allocation */
+            LocalBuffer = RtlAllocateHeap(RtlGetProcessHeap(), 0, Size);
+        }
+        else
+        {
+            /* Reallocation */
+            LocalBuffer = RtlReAllocateHeap(RtlGetProcessHeap(), 0 /* HEAP_GENERATE_EXCEPTIONS */, HeapBuffer, Size);
+        }
+        ASSERT(LocalBuffer != NULL); // We must succeed! TODO: Handle it more properly.
+        HeapBuffer = LocalBuffer;    // HeapBuffer is now reallocated.
+        HeapBufferSize = Size;
+    }
+
+    /* Perform memory copy */
+    EmulatorReadMemory( State, SrcAddress , LocalBuffer, Size);
+    EmulatorWriteMemory(State, DestAddress, LocalBuffer, Size);
+
+    // if (LocalBuffer != StaticBuffer)
+    //     RtlFreeHeap(RtlGetProcessHeap(), 0, LocalBuffer);
+
+    // Note that we don't free HeapBuffer since it's an always-growing buffer.
+    // It is freed when NTVDM termiantes.
+}
+
 VOID EmulatorSetA20(BOOLEAN Enabled)
 {
     A20Line = Enabled;
diff --git a/reactos/subsystems/mvdm/ntvdm/memory.h b/reactos/subsystems/mvdm/ntvdm/memory.h
index c5419cfb67c..431094c985c 100644
--- a/reactos/subsystems/mvdm/ntvdm/memory.h
+++ b/reactos/subsystems/mvdm/ntvdm/memory.h
@@ -55,6 +55,16 @@ EmulatorWriteMemory
     ULONG Size
 );
 
+VOID
+FASTCALL
+EmulatorCopyMemory
+(
+    PFAST486_STATE State,
+    ULONG DestAddress,
+    ULONG SrcAddress,
+    ULONG Size
+);
+
 VOID EmulatorSetA20(BOOLEAN Enabled);
 BOOLEAN EmulatorGetA20(VOID);